The overall goal of this research program is to evaluate the therapeutic potential for buprenorphine and to use animal studies to support its development for depression and anxiety disorders. There is a clear medical need for new drugs that would expand the options for treating comorbid depression and anxiety, especially for the substantial number of patients' refractory to current medications. Buprenorphine is medically available and used safely for the treatment of physical dependence to opioids but has received virtually no attention for the use of psychiatric disorders in nondependent populations. As a mu-opioid receptor (MOR) partial agonist and kappa-opioid receptor (KOR) antagonist, buprenorphine has been studied extensively in models of drug reward, physical dependence, and analgesia. Recent studies highlighting the role of dynorphin in stress have shown that KOR antagonists can produce antidepressant and anxiolytic effects in animal models. The pharmacological profile of buprenorphine as a potent MOR partial agonist and KOR antagonist supports the likelihood that buprenorphine would produce beneficial effects on stress-induced behaviors. Few published studies on the effects of buprenorphine in animal models of depression and anxiety exist to support clinical trials and development or to understand its potential mechanism of action. Taken together, these experiments will establish a basic foundation for considering the development of buprenorphine for new indications in psychiatric disorders and translate to prospective clinical treatment studies of depression and anxiety in treatment-resistant patients.